Let me start off by saying if you're looking for fuel efficiency....you're not going to find it in a Jeep. Add in the 35" tires, lift, etc. and it goes down from there. Possible to gain some of it back by regearing the axles to handle the bigger tires, but not guaranteed.
The main thing you're going to have to worry about with installing bigger tires (35's & 37's) is wearing out the ball joints in the front axle. If you're not planning to off-road it, then you likely don't need to worry about adding a truss and c-gussets to the front axle. They're of course a good idea, especially if you get a wild hair up your butt and decide to take it out and see what it can really do, but not really necessary for on-road use.
Now....if you're really wanting to step up to 37's, you don't need 4" of lift to do it. My Rock Krawler 2.5" Stock Mod, which basically consists of longer travel shocks, taller, heavier duty springs, adjustable front track bar, and front sway bar disconnects netted me about 3" of actual height. The only other you'd need to make 37's fit would be flat flares. Most people (me included) cut their factory plastic flares to accomodate, even when installing 35's. Give's a little more room to stuff the tires into the wheel wells on uptravel. I've since installed Poison Spyder Crusher Flares for a little more protection on the trail and especially aesthetics.
If you're already planning on 35's, it's really up to you as to whether or not you'd want 4.10 gears. For performance, you'd likely want to regear your axles to 4.56's w/ an automatic trans. I'm assuming that's what your wife would want, but I'm not certain. Seems most women prefer an automatic for daily commute, but there are those certain few that like the feel of a manual.
Hope this helps your decision at least a little. Food for thought: I drove my 2011 Unlimited Rubicon w 4.10 gears for about 18 months as a daily with the lift and 37's. Wasn't terrible, but accelaration was pretty poor and of course fuel economy took a pretty big hit. But my rig also has the 3.8L minivan motor that's a pig anyway.
Good luck with your decision and hope to see pics of the new Jeep soon!
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